Providing means for loading a workpiece, positioning and holding the workpiece during machining and unloading the workpiece when the machining is completed is a major problem with most repetitive machining operations. When a workpiece is properly positioned and held, it can be accurately machined. However, time spent in loading, aligning, clamping and otherwise orienting a part with respect to a machine tool, and unloading is time that is not available for the intended machining. A typical solution is to build costly, special one time jigs or fixtures. These are economical only when an extremely long production run is contemplated, and are inefficient when an expensive numerically controlled machine must be used for manufacturing many different parts in relatively short production runs where the cost of large inventories and work in process is excessive.
For certain kinds of machining, CNC lathes are very efficient in metal removal. For example, irregular parts requiring jig boring when done with milling machines, as is the usual case, take ten times longer to machine than when done on a lathe, as lathes are one of the fastest metal removal machines known. Unfortunately, irregular workpieces are difficult to chuck up in a normal lathe so that saved machining time may be expended in excessive loading and unloading time, or costs saved in machining are more than spent in the manufacturing costs of chucking fixtures.
It is economically desirable to keep a machine operator busy all the time. Therefore, if the machining can be accomplished in the time it takes the operator to stack a finished part and ready the next part for machining, the machine and man can operate as a team for the most economical manufacturing. In the past, the only way to get such efficiency out of a man/machine team in slow operations such as jig boring, was to provide multiple machines so that rather than wait during the machining time, an operator could move from machine-to-machine loading them. This requirement that the operator move from machine-to-machine which uses operator time and can present safety hazards. In some environments, it is also undesirable to have an operator away from an operating machine, loading another machine, where a malfunction may not be detected in time to prevent serious damage to the workpiece or the machine. Therefore, there has been a need to provide workpiece retention means which can be installed on lathes and other metal cutting machines and which allow quick and accurate loading for fast machining.